Two New Genera of Stilbellaceous Fungi

Abstract

Two new synnematous genera of the Fungi Imperfecti are described. Dictyocatenulata, with the type species D. alba, is pro- posed for the Dictyosporae group and Hyalotrocophora, with the type species H. lignitalis, is proposed for the Helicosporae group of the Stil- bellaceae. During our investigations on the stilbellaceous Fungi Imperfecti, a fungus possessing hyaline, muriform conidia which occur in long chains has been encountered frequently. Herbarium specimens of this fungus have been identified as Stilbum glomerulisporum Ell. & Everh. Hughes (1953) considered the name to be a nomen nudum. We are unable to find any other record of it. Hughes did not consider the species to be a Stilbum/Stilbella and we concur. The fungus was collected in the Panam'a Canal Zone by E. F. Morris and J. W. Strain in 1964. The only difference between this specimen and the older ones is in the length of the synnemata. The tropical specimens have longer synnemata. The hyaline, muriform conidia of this fungus are quite distinctive. As stated by Hughes, conidia are composed of adpressed and coiled outgrowths of the initial cells . Hughes placed this fungus in Section V of his classification scheme. Section V is characterized by Conidia developing in gradually maturing basipetal series and originating by the meristematic growth of the apical region of the conidiophore in such a way that the chain of conidia merges im- perceptibly with the conidiophore that gives rise to the chain. Although the fungus has not been obtained in culture, this is probably a good conjecture. However, it is entirely possible that these conidia arise as arthrospores which, after formation, continue their maturation by production of the coiled outgrowths which result in multicellular conidia. It is somewhat difficult to ascertain the presence or absence of a meristematic zone from herbarium materials. Hughes' Section VII is characterized by Conidia developing by the basipetal fragmentation of conidiophores of determinate length, and which do, not possess a meristematic zone. Regardless of the production of meristem arthro- spores or arthrospores, the fungus cannot be satisfactorily placed in a known genus and is here described as new.